Yz426 wont run unless choke is out! HELP!

I just installed a quickshot 3 acc. pump cover on a 2002 yamaha yz426.  I started it up and it was running funky and popping, i pulled the choke out and it ran fine.  Now it wont run unless the choke is out, but it runs great with the choke out.  Do i need to jet up due to this upgrade? i put an FMF powercore 4 on it at the same time as the quickshot, some much needed advice would be awesome, PLEASE HELP!

Sounds like it's running lean. I would recommend cleaning or replacing your jets. If that doesn't work maybe try up sizing them. Not sure about the quickshot so maybe that has something to do with it.

Was it sitting for a while before you did the mods?

The pilot jet is the likely culprit.

Just don't run it too hard with the choke out, I believe the bike runs hotter with it out and I was riding my rmz250 one day with the same problem as yours and the pipe started to glow orange, did some research and believe it was the choke being on. Lol

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